Like Amir, Soraya has mistakes from her past, but she is not a complicated character like Amir. How and why does Hosseini create this difference?

Soraya definitely has her own emotional baggage but unlike Amir she is not torn and emotionally stuck. She has a clear sense of love and Duty. She functions as an anchor for Amir, a person that gently leads Amir out of his self-doubt and darkness. She transcends the past and fights for the present. She endears herself to Baba when he is ill and helps navigate through Amir's guilt and regret.